CO2 Conversion Performance of Nickel Catalysts on Varied Supports

An important part of mitigating climate change is reducing atmospheric carbon dioxide (CO₂) and converting it to useful products. An example of this conversion is CO₂ hydrogenation, which uses heterogeneous catalysts and hydrogen to convert CO₂ into valuable fuels and chemicals. Our goal is to design an effective catalyst that facilitates this reaction and investigate the role of the catalyst support on catalyst performance. We investigated how the chemical identity, surface area, and reducibility of the supports influence the performance of a catalyst. First, we measured the CO₂ adsorption capacity of the various oxide supports using thermogravimetric analysis. Al₂O₃ was found to adsorb the most CO₂ (130 μmol CO₂/g support), followed by SiO₂ (95 μmol/g) and CeO₂ (12 μmol/g). Then, we studied the performance of catalysts for the Sabatier reaction: CO₂ + 4H₂ → CH₄ + 2H₂O. Catalysts were placed in a flow reactor and CO₂ and hydrogen were fed over each and the outlet gases were analyzed using gas chromatography. At 300 °C with a CO₂:H₂ ratio of 1:4, Ni/Al₂O₃ was the most active catalyst with a turnover frequency (TOF) of 9.1 x 10^-2­ s^-1 and a CH₄ production rate of 81 μmol/min/g catalyst. Ni/SBA-15 (mesoporous SiO₂) had a TOF of 3.2 x 10^-4 s^-1 and a CH₄ production rate of 0.0813 μmol/min/g catalyst while Ni/SiO₂ (amorphous silica) had a TOF of 6.04 x 10^-3 s^-1 and a CH₄ production rate of 0.0636 μmol/min/g catalyst. We have concluded that Ni/Al₂O₃ is a very active catalyst for CO₂ conversion to CH₄, and future work will seek to further understand the role of the support in catalytic performance.